Create a function

Write JavaScript to modify event properties, validate fields, or enrich event data on a Hightouch Events sync. This guide walks through creating, testing, and connecting a function.

Creating a function

To create a new function, go to Event Collection → Functions and select Create function.

When you create a function, you’ll start with a default function definition, which you can edit to add custom transformation logic.

Keep these requirements in mind:

All code must have a transformEvents function definition, which receives a batch of events, and returns a batch of transformed events
Output events must conform to the core Hightouch Event spec
Event batches can include multiple event types (so make sure to check event.type if you need to handle event types differently)
Batch sizes are variable based on sync volume and event size
Functions time out after 5 seconds of execution time
Events can be filtered out by omitting them from the function return

Testing

Test the function works as expected by using the test panel in the function code editor view.

Modify the input in the test panel, and select Test. Results will be displayed in the output panel, along with any console logs. If the function errors during execution, the error and stack trace will be displayed.

Save & connect

To save a function, hit Save changes at the bottom of the code editor. Upon save, if the function is connected to any event syncs, the new function code will immediately be used.

To connect a function to a sync, use the Connected syncs tab, where you can connect or disconnect a function from a sync. When a function is connected to a sync, events in the target event sync will immediately begin to be transformed by the function.

Note: a function can be connected to multiple syncs, but a sync can only have one function connected to it at a time.

Runtime and dependencies

Functions are executed in a Node.js 22 runtime environment.

Additional available modules:

Crypto is available as crypto
Fetch_API is available as fetch

Debugging

Errors from functions will be displayed in the event sync error logs, along with sample event payloads that received that error.

Other notes

Functions are executed after contract validation (if a contract is defined for the respective event source). This means events blocked by contracts are not able to be transformed using functions.
Use Promise.all to run async code in parallel, reducing the chance of hitting a timeout
If a function errors, the entire batch is failed and will be retried based on the sync retry configuration